Adaptive wing technology, aeroelasticity and flight stability: The lessons from natural flight

Pascual Marques, Elena Spiridon

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This paper reviews adaptive wing morphology and biophysics observed in the natural world and the equivalent adaptive wing technology, aeroelasticity and flight stability principles used in aircraft design. Adaptive wing morphology in birds, including the Harris’ hawk, Common swift, Steppe eagle and Barn swallow, provides excellent examples of aerodynamic and flight control effectiveness that inform the Aeronautical Engineer. The Harris’ hawk and Common swift are gliding birds that change their wing and tail span according to gliding velocity. Inspired by the natural world, effective wing geometry is also modified in aircraft to adjust the aerodynamic load. Bird wings employ an automatic aeroelastic deflection of covert feathers that extend the range of flight configurations and maintain control authority in different flight regimes. Similarly, aircraft structures are not completely rigid and aeroelasticity is important in aircraft. In a Steppe eagle, the alula functions as a high-lift device analogous to the leading edge slats in aircraft wings that allow flight at high angles of attack and low airspeeds without stalling. It has also been suggested that the alula functions as a strake that triggers the development of a leading-edge vortex typical of aircraft delta wings. Sweep-back morphs the hand wing of birds into delta wings that produce lift-generating leading-edge-vortices. A biological high-lift flow-separation control mechanism exists in bird wings, whereby feathers pop up on the wing upper surface to stop the upstream proliferation of separated flow. The equivalent mechanism in aircraft is the self-activated moveable flap that augments maximum lift. Birds exploit stability in flight by morphing the wings and tail. The aeroelastic properties of tail streamers in a Barn swallow trigger an automatic deflection of the tail’s leading edge. This deflection delays flow separation to higher angles of attack, generates higher aerodynamic lift and elicits greater manoeuvrability of the bird. The Aeronautical Engineer may optimise the handling, flying qualities and control of aircraft by mimicking the inherent adaptive morphology, aeroelasticity and flight stability principles observed in nature.
Original languageEnglish
Pages (from-to)25-34
JournalProceedings of the 2013 Maui International Engineering Education Conference
Publication statusPublished - 2013


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